Electric snap switch



Oct. 9, 1962 P. D. GROVER ETAL 3,

ELECTRIC SNAP SWITCH Filed Sept. 1, 1959 United States Patent ()fifice 3,057,982 ELECTRIC SNAP SWITCH Philip D. Grover and BEilen S. Grover, Chicago, Ill., as-

signors to Grover Products Corporation, a corporation of Illinois Filed Sept. 1, 1959, Ser. No. 837,459 8 Claims. (Cl. 2tl0138) This invention relates to an electric snap switch and more particularly to a simply constructed snap switch having a compound action and a stressed blade switch which may be thermally responsive.

An object of this invention is to provide a new and improved electric snap switch with compounded action in which the switch operation in shifting from one position to another is accomplished substantially instantaneously and without gradual reduction in contact pressure.

In the art of snap action switches to make, break or transfer an electrical circuit over-center devices of one type or another have been commonly used to snap a blade carrying a contact from engagement with one normally closed contact to engagement with another fixed contact or contacts to effect the desired switching action. The snap action has the advantage of rapidly moving the contacts to minimize arcing and consequent erosion thereof. These devices have the disadvantage that the pressure existing between the movable contact and the fixed contact drops toward zero as the actuating member of the over-center or toggle device approaches the critical point defiining the point of snap action. This can result in a condition referred to as dead break in which the contact carried on the blade actually separtes from the fixed contact and the blade may float prior to completion of the snapping of the switch. This dropping of the contact pressure is also troublesome in applications where the actuating pressure for snapping the switch is slowly applied. This reduction of pressure effects the reliability of the switch and subjects it to faulty operation in response to vibrations and also limits the amount of amperage which can be carried by the switch.

Therefore, another object of my invention is to provide a snap action switch avoiding the foregoing problems in which a compounded snap action is obtained and comprises a primary snap mechanism and a secondary snap mechanism both of which are arranged to snap over center and the primary snap mechanism when shifted over center snaps the secondary snap mechanism. Even though a shifting force may be gradually applied to the primary snap mechanism, the secondary snap mechanism carrying the electrical contact retains full pressure engagement with the circuit fixed contact and substantially instantaneously shift its position in response to shift of the primary snap mechanism.

Another object of the invention is to provide a snap switch with the compounded snap action as defined in the preceding paragraph wherein the primary and secondary snap mechanisms are formed from a single piece of material to have the fewest possible number of parts to improve the reliability factor and also maintain the cost of manufacture at a minimum.

Another object of the invention is to have a snap switch as defined in the preceding para-graph in which the force for shifting the switch is provided by the switch itself. At least a part of the switch is constructed of thermally responsive bimetal which in response to a predetermined change in the ambient temperature builds up sufficient force within the switch to overcome the stress forces in the switch blade and change the configuration of the switch. This provides a positive accurate controllable means for switching a circuit upon a change in temperature and thus is useable as a thermal overload circuit breaker as in the case of overheated motor and the like.

3,057,982 Patented Oct. 9, 1962 Further objects and advantages will become apparent from the following detailed description taken in connection with the accompanying drawings in which:

FIG. 1 is a perspective view of the snap switch with theucasing omitted and with parts shown diagrammatica y;

FIG. 2 is a front elevational view of the structure shown in FIG. 1 and with the switch blade shown in one normal position;

FIG. 3 is a view similar to FIG. 2 but showing the primary snap mechanism shifted and with the secondary snap mechanism still in its original position;

FIG. 4 is a view similar to FIGS. 2 and 3 but showing the switch blade in fully shifted position and in an alternate position from that shown in FIG. 2;

FIG. 5 is a perspective view of a double break snap switch with the casing omitted and parts shown diagrammatically; and

FIG. 6 is a schematic of a circuit embodying the snap switch of FIG. 5.

While this invention is susceptible of embodiments in many different forms, there is shown in the drawings and will herein be described in detail an embodiment of the invention together with a modification thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiment illustrated. The scope of the invention will be pointed out in the appended claims.

As shown in FIGS. 1-4 the snap switch comprises a base it which supports through a stem 11 and a mounting screw Illa a blade, indicated generally at 12, having a primary snap mechanism, indicated generally at 13, and a secondary snap mechanism, indicated generally at 14. Each of the snap mechanisms 13 and 14 has a section with a generally triangular configuration with a base leg 15 common to both sections and a pair of side legs. The side legs for the primary snap mechanism 13 being identified at 16 and 17 and the corresponding legs of the secondary snap mechanism 14 being identified at 18 and 19.

Each of the snapmechanism sections is stressed to give the blade and sections a generally concave con figuration as shown in FIG. 2. This is accomplished by distorting the blade from its original planar form by shortening the side legs 16 and 18 by bending a wave or corrugation 20 and 21, respectively, therein.

The blade 12 carries a contact 22 and is formed of electrically conducting material whereby the switch is placed in circuit through a line 23 passing through the mounting stem 11 for the blade and one or the other of a pair of fixed contacts 25 and 26 carried by the switch housing (not shown). With the contact 22 shown in the position of FIG. 2 the circuit is made through the contact 25 having a line 27 extending therefrom and with the blade in the position of FIG. 4, the contact 22 is in engagement with the contact 26 having a line 28 exending therefrom. Thus the switch may shift a circuit or either of the contacts 25, 26 may be out of the circuit whereby when the contact 22 engages therewith the circuit is broken.

Specifiically, the primary snap mechanism 13 has a corner 39 to which a force may be applied and as shown in FIG. 3 the application of the force in the direction of the arrow 6 snaps the primary snap mechanism. An area 31 of the blade constitutes a force applying section of the primary snap mechanism as well as a driving section of the secondary snap mechanism. When the primary mechanism has snapped, the area 31 is depressed to snap the secondary snap mechanism to place the switch in the position shown in FIG. 4. The movement of the switch from the position of FIG. 3 to that shown in FIG. 4 is substantially instantaneous so that the condition illustrated in FIG. 3 is not ordinarily visible but is shown for the purpose of clarity in the description.

The blade will maintain the position shown in FIG. 4 so long as the force is applied to the corner 30 of the primary snap mechanism and once the force is released the blade will return to the position of FIG. 2. It should be noted that the blade need not be supported as shown in FIGS. l-4 but may merely be restricted at a corner for limited movement and then supported centrally.

The driving force for the snap mechanism may be externally applied by any suitable mechanism including a separate piece of thermally responsive bimetal located so as to act upon the corner 30 of the primary snap mechanism. A preferred embodiment is shown in FIGS. 1-4 in which a part of the primary snap mechanism is itself formed of bimetal and thus a strip 31a of bimetal is attached to the main blade structure and specifically the blade leg 17 by suitable means, such as spot welding. An alternate construction would have the entire blade or the primary snap section formed from bimetal to thus accomplish the same result of having internal forces built up in response to a predetermined change in ambient temperature to shift the switch to an alternate position.

As an example, the main blade 12 may be formed from brass while the added strip of material 31a has a relatively low thermal coefficient of expansion. The strip 31a may be a material such as Invar which is an iron and nickel composition.

The snap switch shown in FIGS. 1-4 is a single break switch while a double break switch is shown in FIG. 5. The latter embodiment constitutes a doubling of the snap switch shown in FIGS. 1-4 as indicated by the application of the same reference numerals to the similar parts disclosed in FIG. 5. With the switch of FIG. 5 the application of a force to the corner 30 results in a shift in position of the area 31 of the switch which upon snapping over center instantaneously snaps the switch blade sections carrying the contacts 22.

The schematic of a circuit embodying the double compound snap switch of FIG. 5 is shown in FIG. 6 in which it will be noted that the two contacts 22 may shift between a position engaging fixed contacts 25 or a position engaging fixed contacts 26.

We claim:

1. An electric snap switch comprising, in combination, a one-piece blade of electrically conducting material having a pair of triangular sections with one defining a primary snap mechanism and the other a secondary snap mechanism, said triangular sections having a common base leg and each having a pair of side legs, a corrugation in one of the side legs of each section to place said blade in a generally concave stressed configuration, means supporting said blade for shift to a convex configuration in response to a force moving a corner of said primary snap mechanism, and a switch contact carried on a section of the secondary snap mechanism whereby a force moving a corner of the primary snap mechanism snaps its triangular section to a convex configuration which snaps the, secondary snap mechanism section to a convex configuration to shift said contact to an alternate position.

2. An electric snap switch comprising, in combination, a one-piece blade having a pair of sections with one defining a primary snap mechanism and the other a secondary snap mechanism, said sections having a common base leg and each having a pair of side legs, each section being separately stressed by a corrugation in a side leg to place said blade in a generally concave configuration, means supporting said blade for shift to a convex configuration, and a switch contact carried on a switch section of the secondary snap mechanism whereby a force moving the primary snap mechanism to a convex configuration snaps the secondary snap mechanism to a convex configuration to shift said contact to an alternate position.

3. An electric snap switch as defined in claim 2 in which said blade is constructed at least in part of thermally responsive bimetal whereby a predetermined change in ambient temperature will induce internal forces in the blade sufficient to shift said snap mechanisms.

4. An electric snap switch as defined in claim 2 in which a double break switch is provided by having two of said pairs of sections as a single blade with a side leg of each primary snap mechanism being a common memher.

5. An electric snap switch having a blade construction stressed to a concave configuration with a primary snap mechanism integral and in series with a secondary snap mechanism and formed from a single piece of electrically conducting material, said secondary snap mechanism having a totally enclosed aperture and switch section, said primary snap mechanism having a separate totally enclosed aperture and a force applying section adjacent an actuatable section of the secondary snap mechanism, and a driving section on said primary snap mechanism whereby a force shifting said driving section results in substantially simultaneously snapping said force applying section which resultantly shifts said actuable section and snaps said switch section to an alternate position.

6. A compound snap switch having an integral primary snap mechanism and a secondary snap mechanism each of a similar stressed blade concave configuration and at opposite sides of a blade section common to both snap mechanisms, said secondary snap mechanism carrying a switch contact and having a section responsive to a force application to shift over-center and shift said contact, said primary snap mechanism having a first section responsive to a force application to shift over center and a second section shiftable over center and positioned to operate sad secondary snap mechanism. 7. A compound snap switch as defined in claim 6 in which said first section of the primary snap mechanism is composed of bimetal whereby said force for shifting is internally generated in response to a temperature change.

8. An electric snap switch having a blade with two openings therein substantially equally surrounded by body parts of said blade, means associated with a portion of said blade for selectively completing a circuit, a first part of the blade body surrounding one opening being shortened by a corrugation therein to place a stress in said first part of the blade body and distort said part into a concave configuration, means supporting the blade for snap to a convex configuration, and a second part of the blade body surrounding the other opening being similarly shortened by a corrugation therein on one side of the opening, adapted whereby an external force applied to the first part of the blade body will cause it to snap from its normal position to an alternate position, such snap inducing a corresponding alternate snap in the second part of the blade body.

References Cited in the file of this patent UNITED STATES PATENTS 2,194,999 Clark Mar. 26, 1940 2,487,374 Riche et al. Nov. 8, 1949 2,630,504 Burch et al. Mar. 3, 1953 2,700,079 Haydon Jan. 18, 1955 2,777,032 Burch Jan. 8, 1957 2,834,853 Hood May 13, 1958 2,899,512 Burch Aug. 11, 1959 

